The invention relates to a valve, especially a solenoid valve, with a tappet movable along a valve axis, with a valve seal disposed concentrically on said tappet, and with said seal abutting an associated sealing surface endwise.
Valves of this type are known in various designs. As in solenoid valves, the tappet can be actuated by a magnetically operated plunger, or by a piston, actuated by a pressure medium. Valves of this type, generally designated as flat-seat valves, have the disadvantage that when switching forces increase, i.e., either when the pressure of the medium to be controlled increases or the throughput cross section is increased, either stronger drives are required to control the switching forces, which also entails an increased strength for the valve construction, or additional electrical devices must be provided, the latter also requiring reinforcement of the valve components.
An object of the present invention is to design a valve of the type described hereinabove in such manner that significantly higher pressures or higher throughput cross sections can be controlled by retaining the same dimensions for the drive devices, without costly additional devices being required. The invention attains this object by providing that the valve seal, as a separate component, is held against the tappet by an eccentrically mounted tilting axis and a return spring. By virtue of this design, the valve seal does not lift over the area of the entire seat when the valve opens, but is initially lifted at one side only, so that the driving forces required therefor need be only approximately half as great as those which are conventionally required in previously known valves. When the valve seat is raised slightly at one side, the pressures equalize and the remainder of the opening movement may be accomplished with low driving forces.
In particularly advantageous preferred embodiments of the invention, the valve seal tilting axis and the return spring are in the form of a connecting spring, said connecting spring having at least one spring arm extending radially with respect to the valve axis and a loop connected therewith, whereby each of these two parts is attached to one of the components to be connected with one another. This design allows a very simple and inexpensive construction.
The connecting spring is provided with two loops arranged symmetrically with respect to the spring arm, said loops being gripped in grooves in the valve seal in one preferred embodiment. In this embodiment, the tappet is preferably advantageously provided with a guide surface for the valve seal, against which the valve seal is pressed by the connecting spring. This design makes it possible to achieve simple but effective guidance of the valve seal relative to the seat in a relatively simple fashion, without losing the advantageous effect when the valve seal is raised.
In a very simple preferred embodiment, the connecting spring is a loop spring formed in one piece from a spring wire, the loop fitting the circumference of the valve seal being gripped in such manner that it snaps into the groove in the valve seal. This design also allows a very simple installation of the valve seal on the tappet, since it is sufficient to push the snap spring through both parts. In order to facilitate this assembly step, the ends of the loops can be bent outward.
In order to mount the snap spring reliably on the tappet, the spring arm extends between the loops, said arm consisting of two wire loops arranged parallel to one another which are held on the tappet by a locking plug. The locking plug is inserted centrally into the recess in a collar, said collar being mounted on the tappet and being provided with the guide surface for the valve seal. The collar has an opening extending diametrically through it, in which the spring arm is firmly gripped. This collar can be screwed onto the tappet, so that the manufacture of this part poses no difficulty whatever. Naturally, the valve seal must also be provided with a diametrally extending opening, whose cross section must be selected so that sufficient play for movement is provided for the unilateral (initial lifting at one side) lifting movement.
The invention can also be implemented in a quite different embodiment, wherein the loops of the connecting spring form a wire ring connected with the tappet, said ring fitting from the inside into a groove in a diaphragm which is used as the valve seal, tensioning said diaphragm. This design is very simple to implement and is suitable for a large number of applications, especially for controlling liquids containing calcium, because the utilization of the tensioned diaphragm allows calcium deposits on the diaphragm and the tensioning guide parts to be avoided. The wire ring is preferably made integral with the return spring arm, said arm being guided in turn to a plunger forming the tappet and being fastened thereto, whereby the diaphragm can also be pressed by a compression spring against the sealing surface. This embodiment also has the considerable advantage that the switching forces that must be applied, by comparison with previously known valves, may be kept low, despite the higher pressures of the medium to be controlled or increased throughput cross sections.
With respect to the embodiment referred to above for controlling liquid containing calcium, hereinafter the "self-cleaning embodiment", it is noted that solenoid valves are known which are also used for controlling fluids which have a high calcium content. When conventional plunger valves are used under these conditions, wherein a sealing element fits into a matching valve seat and is controlled by the energization of an electromagnet, the danger arises (especially after a prolonged operating period) that the valve becomes leaky, because deposits such as calcium deposits are formed in the sealing area which prevent smooth functioning. These disadvantageous phenomena occur in particular in solenoid valves in coffee makers, water heaters, washing machines, and the like.
Diaphragm valves are also known wherein a diaphragm mounted in a housing separates the housing chamber in which the plunger drive is located from the flow chamber. The diaphragm is pressed against the edge of a valve seat by the movement of the plunger. These features have the advantage that they do not exhibit such a rapid tendency to develop calcium deposits in the vicinity of the moving diaphragm, but do suffer from the considerable disadvantage that the diaphragm must be tensioned against the water pressure. This requires either high tensioning pressures which make powerful magnetic forces necessary, or there will be a danger of the diaphragm opening as a result of pressure fluctuations in the medium being controlled.
Therefore, a further object of the self-cleaning embodiments of the present invention is to provide a solenoid valve which is especially suited for controlling fluids containing calcium, and is therefore designed in such fashion that deposition of calcium is largely avoided, but which is relatively simple in construction so that it may be employed economically.
The invention contemplates attainment of this further object in this self-cleaning embodiment by making the sealing element in the form of a diaphragm or the like cooperating with the end of an outlet stub projecting into a valve housing with the sealing element mounted in a holder which extends outside the sealing outline of the outlet stub and with the holder being connected to a movable plunger. This design ensures that a certain shearing effect takes place between the membrane and the sealing edge during each sealing process, because the diaphragm is pulled outward from its mount over the sealing edge (due to the holder extending peripherally outside the sealing outline of the outlet stub). The diaphragm need not be moved against the water pressure to the closing position so that low magnetic forces will suffice to actuate the valve. Nevertheless, a self-cleaning valve is produced which is particularly applicable for controlling liquids containing calcium.
It is advantageous according to particularly preferred self-cleaning embodiments of the invention to have the connection between the diaphragm and the solenoid plunger in the form of the wire ring, because this ensures a very inexpensive yet very effective design. This wire ring is preferably mounted in the groove formed by a projecting edge of the pot-shaped diaphragm, so that separate fastening devices are unnecessary. In this especially advantageous embodiment, this wire ring is made from a wire shaped into a loop, one end of which is bent radially with respect to the center of the ring and then bent toward the plunger, so that a single piece of wire connects the plunger to the diaphragm. This design also has the advantage that relativey thin wires can be used which are subjected to certain vibrations during each switching process, so that calcium deposits on these parts are also largely avoided. If the end of the wire is bent toward the center from the circumference of the loop in the plane of the loop, it is advantageous to install a twisted ring as a spacer between the diaphragm and the wire ring, so that the connecting wire to the plunger does not contact the surface of the diaphragm during the switching process.
In order to ensure sufficient sealing force in this self-cleaning embodiment, the edge of the diaphragm is preferably pressed by a compression spring against the end of the outlet stub, said compression spring having its other end abutting the other side of the housing. The plunger than operates against the action of this compression spring as the valve opens. This compression spring need not be made very strong because the diaphragm is also subject to the pressure from the fluid being controlled and is pressed against the seat when in the closed position. The compression spring can, however, exert a certain guiding effect, so that it will suffice to make the connection with the plunger consist only of the thin wire section mentioned above.
This preferred self-cleaning embodiment of the invention provides a highly advantageous possibility for preventing calcium deposition in the vicinity of the plunger, by virtue of the fact that the compression spring abuts the housing with a disk interposed, said disk leaving only a small opening through which the wire to the plunger passes, and otherwise separates the valve chamber in the housing from the operating chamber of the plunger. In the operating chamber of the plunger, therefore, a volume of fluid is moved about which corresponds to the small volume of the wire which is submerged. There is substantially no additional exchange with the fluid chamber which contains the calcium. In this manner, the tendency toward calcium deposition may be reduced, whereby this design feature is also contemplated for use in valves which do not have a diaphragm as a sealing element, according to other preferred embodiments.
Yet another advantageous preferred embodiment of the invention is contemplated which provides that the valve seal consists of an elastically flexible plate, said plate being held against the tappet by fastening elements, said elements projecting at least at one point on the circumference of the plate, out of the plane radial to the tappet axis in the direction of the tappet, in which the other contact points of the fastening elements are disposed on the edge of the plate. This results in an advantageous embodiment if the plate is part of a cap articulated with its open end on the tappet and the fastening elements are in the form of a ring which grips behind a bead on the edge of the cap, said ring being bent outward at one point, upward toward the tappet. In this embodiment also, an eccentric lifting action is created when the valve seal is raised, so that the same advantages may be obtained as were listed above.
For small specified widths and limited available space in the valve body, an embodiment is particularly to be recommended in which the ring of the outwardly turned-over edge is a bushing attached to the closed end of the tappet. The bushing can then accept a compression spring in its interior, said spring abutting the closed side of the elastic cap. For large specified widths, a valve seal can be obtained very simply if the plate is a valve plate gripped elastically at the lower edge of a bushing. This valve plate can either be made elastic itself or may be pressed against an elastic seal by a compression spring according to alternative contemplated embodiments, said seal forming the seat on an outlet stub. An advantageous embodiment is ensured if the lower edge of the bushing is provided with an inwardly directed collar, against which the valve plate rests, and if the collar is elevated at one point to a greater extent relative to the closed part of the bushing. The raised part will then lift the valve plate unilaterally (from one side) as it rises, and the advantageous effects set forth above will be achieved despite the simplicity of the design.
Embodiments of the invention are also contemplated, wherein, instead of the inwardly directed collar of a bushing, pluralities of claws uniformly distributed around the circumference are provided, at least one of which claws is bent upward more than the others. In both cases, a compression spring acting on the valve plate is advantageously disposed inside the bushing, said spring forming the non-positive connection between the components.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings, which show, for purposes of illustration only, several embodiments in accordance with the present invention.